The present invention relates to a web tensioning roller for use in the manufacture of and use of continuous web substrates, and in particular, to such a device that automatically adjusts its orientation to equalize the tension across a moving web.
In the manufacture or combining processes of metallic, plastic, woven, non-woven, paper, and webs of other substances, the web substrate must contact idler rolls to be positioned within the manufacturing process. If the tension exerted by the web substrate on one end of the idler roll is greater than the tension exerted on the other end of the same idler roll, a variety of problems result that affect substrates in different ways.
The causes that contribute to uneven tension may be inherent to the web substrate itself as having occurred during its formation, or the uneven tension may be mechanically induced by machine misalignments. The result of poor tension control is a finished product of lower or unacceptable quality. The finished product may be stretched, warped, or be subjected to nonuniform application of a variety of coatings and adhesives. Stretching generally deforms the substrate permanently and may render it useless as a finished product.
Warp is most common in paper products and is a result of uneven tension across a web experienced during the heating application. This uneven heat application causes more moisture to be evacuated from one side of the web than the other. The result is that one side of the web will shrink more than the opposite side and cause a curve to occur at the combining process. If the proximity of the substrate to laminating, adhesive, printing, and other coating applications is not maintained the application will be uneven and result in an inferior finished product. One way to avoid this is by controlling tension across the web to insure that the substrate maintains a uniform distance to or tension against the application.
By controlling the tension across the width of a substrate the web will be less susceptible to weaving. Weaving in continuous webs or belts is caused by the substrate attempting to pull to the high tension side during machinery operation and is most common during equipment speed changes. By effectively equalizing the tension across the web this condition is nullified. This control also expands the application of this device to assist in maintaining control over the direction of travel of belting and other like conveyance methods.
What is needed is a web tension control device that automatically equalizes the tension across a web during the manufacturing process.